How to get active application?

Question

I develop an UDF in C#:  

public string GetActiveSheetName()
        {
            string Caller = null;
            Excel.Application oExcel = Marshal.GetActiveObject("Excel.Application") as Excel.Application;
            Caller = oExcel.ActiveSheet.Name;
            return Caller;
        }

 

This works fine if there is only one Excel process running. But if I have two or more instances of Excel are running, it still return first excel application's active sheet name.

Answer 1

I've been working this problem since your previous posting.  After a few days of trying I finally got all the code to work.  I had to use a number of Winn32 API to get it to work.  Here are the steps I used.  I not sure if there is an easier way to do this.

1) You need to find all the Excel.exe processes.  This was pretty easy to do.  I used the Net Library function Process.GetProcessesByName(@"excel") which returns an array of Processes

2) I then checked that the Excel.exe window was the active window using Win32 API user32.dll function IsWindowVisible.

3) I then had to write another function EnumChildWindows(ExcelWin, cb, ref hwndChild) which uses the Win32 API User32.dll function GetClassName().   I needed the child window to be able to extract the excel application from the window.

4) Next I used the Win32 API Oleacc.dll function AccessibleObjectFromWindow  to get the excel object from the window.

5) Finally I overload the window object to an excel object and get the sheet name.

 

//using System.Runtime.InteropServices;
        //using System.Diagnostics;

        public delegate bool EnumChildCallback(int hwnd, ref int lParam);

        [System.Runtime.InteropServices.DllImport("User32.dll")]
        public static extern bool EnumChildWindows(IntPtr hWndParent, EnumChildCallback lpEnumFunc, ref IntPtr lParam);

        private static EnumChildCallback cb;


        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool IsWindowVisible(IntPtr hWnd);
  

        [DllImport("Oleacc.dll")]
        private static extern int AccessibleObjectFromWindow(
            IntPtr hwnd, uint dwObjectID, byte[] riid, [MarshalAs(UnmanagedType.IUnknown)]ref object winobj);

        [DllImport("User32.dll")]
        public static extern int GetClassName(
            int hWnd, StringBuilder lpClassName, int nMaxCount);

        
        public static bool EnumChildProc(int hwndChild, ref int lParam)
        {
            StringBuilder buf = new StringBuilder(128);

            GetClassName(hwndChild, buf, 128);
            if (buf.ToString() == "EXCEL7")
            {
                lParam = hwndChild;
                return false;
            }
            return true;
        }

        public static string GetActiveSheetName()
        {
            
            string activesheetname = null;
            IntPtr activeAppWindow = IntPtr.Zero; 
            IntPtr ExcelWin;
            

            Process[] ExcelProcesses = Process.GetProcessesByName(@"excel");
           
            foreach(Process MyProcess in ExcelProcesses)
            {
                ExcelWin = MyProcess.MainWindowHandle;
                IntPtr hwndChild = (IntPtr)0;
 

                cb = new EnumChildCallback(EnumChildProc);
                EnumChildWindows(ExcelWin, cb, ref hwndChild);

            
                    if (IsWindowVisible(ExcelWin))
                    {
                   
                    
                       const uint OBJID_NATIVEOM  = 0xFFFFFFF0;
                       Guid IID_IDispatch = new Guid("{00020400-0000-0000-C000-000000000046}");
                       object winptr = null;
                    
                   
                        int As = AccessibleObjectFromWindow(
                            hwndChild, OBJID_NATIVEOM, IID_IDispatch.ToByteArray(), ref winptr);
                        Excel.Window excelwin = (Excel.Window)winptr;
                        Excel.Application XlApp = excelwin.Application;

                        Excel.Worksheet sht = (Excel.Worksheet)XlApp.ActiveSheet;
                        activesheetname = sht.Name;


                        break;

                }
               
            }
            return activesheetname;
        }    

 

 

 

 

 

 

 

 

Answer 2

Thank you very much!

If there is only one instance, it works fine. But if there are more than one instance, it doesn't work fine.